ORIGIN OF THE CEREBRAL NERVES. 491 



myself that even those fibraa rectse of the raphe', which, pro- 

 ceeding' from the region of the abducens-facialis nucleus, run 

 obliquely downwards towards the medulla oblongata, curve 

 round at the lower border of the pons, and run with the 

 pyramids into the eras cerebri. 



The abducens-facialis will consequently be subject to the 

 crossed influence of the centres of origin of the crusta of the 

 eras cerebri. 



The roots of the sixth proceed from this nucleus in the form 

 of fine separate fibres from a portion of the pons, of 1*4 milli- 

 meters in height, and, running in an antero-posterior direction 

 parallel and close to the raphd, reach the posterior division of 

 the pons, and pass from thence obliquely downwards to their 

 well-known position in the basis cerebri. The external fasci- 

 culi of the central root of the abducens, that lie in the anterior 

 part of the nucleus, obviously proceed from its nerve corpuscles, 

 and form arches directed internally. The internal fasciculi, 

 however, appear to embrace the nucleus as a compact me- 

 dullary layer in which only a few nerve corpuscles are dis- 

 tributed. I believe I have satisfactorily convinced myself 

 that these fasciculi also simply proceed from the same nucleus, 

 although they describe almost a complete circle around their 

 origin. 



The nucleus of the sixth, with the fasciculi of its root, would 

 consequently represent a glomerulus or knot analogous to the 

 nucleus of the hypoglossus (fig. 258, xn). 



The central extremity of this knot, like the latter, would be 

 found in those fibrse rectae of the raphe' which enter the 

 nucleus of the sixth as posterior fibrse arcuatse. These fasciculi 

 of the crus cerebri encircle the nuclear mass on its anterior 

 and external surfaces, are interrupted by the nerve corpuscles, 

 and following the convolution of the knot pursue their course 

 to the root fasciculi by means of which the circle which they 

 form around the nucleus is completed in its posterior and in- 

 ternal parts. The difficulty that is experienced in bringing into 

 view the continuity of this course in sections is due especially 

 to the circumstance that the course pursued by each fibre of 

 this knot in the raphe belongs to lower planes of section than 

 the root extremities of these fibres; and hence in the right half 



